Fabrication and characterization of temperature-, pH- and magnetic-field-sensitive organic/inorganic hybrid poly (ethylene glycol)-based hydrogels

In this paper, we successfully fabricated a new kind of multiple stimulus-responsive organic/inorganic hybrid hydrogels by combining dual stimuli-responsive poly (2-(2-methoxyethoxy) ethyl methacrylate-co-oligo (ethylene glycol) methacrylate-co-acrylic acid) (PMOA) hydrogel with magnetic attapulgite/Fe3O4 (AT–Fe3O4) nanoparticles. First, the magnetic nanoparticle was prepared via co-precipitation technique in aqueous suspension of purified attapulgite. The obtained AT–Fe3O4 nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and vibrating sample magnetometer. Compared with pure attapulgite, the AT–Fe3O4 exhibited better superparamagnetic properties. Then, the AT–Fe3O4 was introduced into the dual-responsive (temperature and pH) PMOA hydrogel network by in situ polymerization. The morphology, responsive behaviors and tensile properties of the prepared hydrogels were systematically characterized by field emission scanning electron microscopy, vibrating sample magnetometer, swelling/re-swelling behaviors and tensile testing. The results showed that the AT–Fe3O4 nanoparticles were well dispersed in the hydrogel matrix, and the multi-functional AT–Fe3O4/PMOA nanocomposite hydrogels had not only temperature/pH sensitivity and good mechanical properties, but also magnetic functionality. The tunable superparamagnetic behavior of these hydrogels depended on the amount of AT–Fe3O4. In addition, the multi-functional AT–Fe3O4/PMOA nanocomposite hydrogels can continue to swell under an alternating magnetic field after equilibrium swelling in deionized water.